A communications method as a successor of W-CDMA and HSDPA, namely, Long Term Evolution (LTE) has been considered by a W-CDMA standardization organization 3GPP. As a radio access method, Orthogonal Frequency Division Multiplexing (OFDM) is under consideration for downlink, and Single-Carrier Frequency Division Multiple Access is under consideration for uplink (see 3GPP TR 25.814 (V7.0.0), “Physical Layer Aspects for Evolved UTRA,” June 2006, for example).
In OFDM, a frequency band is divided into plural narrow frequency bands (sub-carriers), and data are placed on the respective divided frequency bands, so that the transmission is carried out. The sub-carriers are densely arranged in a frequency direction, allowing the sub-carriers to be partly overlapped without causing interference, thereby realizing high speed transmission and improving frequency usage efficiency.
In SC-FDMA, a frequency band is divided into plural narrow bands, and different narrow bands are used by different users, so that interference between the user terminals can be reduced. According to SC-FDMA, which is characterized in that variations in the transmission electric power are reduced, a large coverage area and low energy consumption can be realized.